1. Field of the Invention
This invention is directed to a resistive ribbon for thermal transfer printing, and a method of printing employing that ribbon. Specifically, a ribbon bearing a resistive layer of non-stoichiometric metal silicide which may be connected to a voltage controlled power supply to cause resistive heating in the resistive layer at selected points, thereby heating a layer of fusible ink at those points corresponding to area resistively heated is disclosed herein. This ribbon allows for efficient, economical thermal transfer printing, where high quality, low volume printing is desired.
2. Description of the Prior Art
The art of non-impact printing is becoming increasingly popular as a method for producing high quality written materials, where such characteristics are desirable. Among the non-impact printing modes, thermal transfer printing has proved particularly desirable where high quality, low volume printing is necessary, such as in computer terminals and typewriters. In thermal transfer printing, ink is printed on the face of a receiving material whenever a fusible ink layer brought in contact with the receiving surface is softened by a source of thermal energy. The thermal energy is supplied from a source of electricity, the electrical energy being converted to thermal energy.
One device employed for thermal transfer printing is a thin ribbon, or resistive ribbon, which bears a layer of fusible ink that is brought into contact with the receiving surface on one side, and on the other side of the ribbon is a layer of resistive material which is typically brought in contact with an electrical power supply and selectively contacted by a thin printing stylus at those points opposite the receiving surface that are desired to be printed. When the resistive layer is thus contacted, resistive heating results, which heating results in the local melting of the fusible ink layer. Such a ribbon is generally discussed in U.S. Pat. No. 3,744,611, Montanari et al.
Prior art attempts to provide such a resistive ribbon for thermal transfer printing have typically encountered significant limitations. Among other obstacles, the material selected to support both the fusible ink and the resistive layer has been difficult to adhere to the other layers of the ribbon. Additionally, the same supporting layer may act as a thermal barrier to the transfer of heat from the resistive layer to the ink layer, thereby frustrating the printing process. Additionally, the resistive layers of these ribbons, typically graphite dispersed in a binder, required so much energy for heating that the layer might be burned through before printing occurred.
Accordingly, it is the object of this invention to provide a resistive ribbon for thermal transfer printing and a method for using that ribbon which results in economical, efficient and high quality printing.
Another object of this invention is to provide a ribbon which requires much less energy for resistive heating to achieve printing.
Still a further object of this invention is to provide a film that is thinner than the prior art, so that more ribbon can be packed into a single unit.
Yet a further object is to provide a resistive layer that will not release toxic materials or burn through.
Yet another object of this invention is to provide a resistive layer employing inorganic media such that the use of toxic solvents in manufacturing may be avoided.